Automated test equipment (ATE) enables electronic testing, in volume, of units-under-test (UUTs) in a reliable and consistent manner. Examples of UUTs include semiconductor devices (e.g., processors, application specific integrated circuits, field programmable gate arrays, etc.), circuit boards (e.g., motherboards, daughter cards, multi-chip modules, etc.), and the like.
The equipment, which is commonly referred to as an automatic test system or simply tester, typically includes an instrumentation and support assembly (hereinafter simply referred to as the instrumentation assembly) and a computer. The instrumentation assembly typically includes circuit board modules which vary in design and function. For example, some modules specialize in driving certain types of signals onto the UUTs (e.g., digital signals, analog signals, radio frequency signals, combinations thereof, etc.). Other modules specialize in detecting such signals from the UUTs. Yet other modules provide power supply signals, overhead, timing, etc. Typically, the instrumentation assembly further includes a card cage for holding the modules and a backplane for connecting the modules to the computer. Once an appropriate combination of these modules is properly installed within the card cage of the instrumentation assembly, the computer communicates with these modules through the backplane to coordinate their operation and thus perform comprehensive testing of the UUTs. The computer also plays an effective role in analyzing and evaluating the results of such testing.
In general, manufacturers attempt to provide automatic test systems which are easily re-configurable for enhanced flexibility. To this end, some tester manufacturers (i) provide the card cage of the instrumentation assembly with universally-sized card cage slots and (ii) size the circuit board modules to fit into any of the universally-sized card cage slots regardless of function. As a result, customers of such automatic test systems are then capable of installing different combinations of the circuit board modules into the card cage slots and thus are capable of performing a variety of different tests using the different combinations of modules, e.g., different tests on the same UUTs, different tests on different UUTs, etc.
Although the card cage slots of the above-described card cage are universal in size (i.e., each card cage slot permits insertion of any circuit board module regardless of function), the configurations of backplane connectors within the card cage (i.e., the corresponding connectors on the backplane which mate with connectors on the circuit board modules) may not be uniformly positioned from card cage slot to card cage slot. Accordingly, some circuit board modules will not properly connect in certain card cage slots. Moreover, for any given slot, even if the backplane connectors properly match the circuit board connectors of a particular circuit board module, there are occasions when that module may still be unable to properly install into that slot due to a component height restriction (e.g., a component of the module may be too tall thus providing an obstruction that prevents that module from properly inserting all the way into that slot).
To prevent insertion of a circuit board module into an incorrect card cage slot and thus to avoid damage to either the module (e.g., connectors or tall components of the module) and/or the backplane connectors housed within the card cage, tester manufacturers typically provide keying mechanisms at the back end of the card cage in the area of the backplane. That is, each card cage slot has a unique physical keying feature that enables only certain modules to fully insert into that slot. In one approach, the tester manufacturer provides the backplane connectors with alignment pins and the circuit board connectors with alignment holes (or vice versa), thus only allowing a module to fully install into the card cage when the alignment pins properly align with the alignment holes. If the alignment pins do not match with the alignment holes, the alignment pins provide mechanical interference against the module and the module is incapable of fully inserting into the card cage. In another approach, the tester manufacturer provides an alignment notch or indentation at a particular location along the connecting edge of the module and an alignment tab along a location of the backplane thus only allowing a module to fully install into the card cage when the alignment notch location matches the alignment tab location. If the alignment notch location does not match the alignment tab location, the tab provides interference against the module thus preventing the module from inserting further into the card cage. As a result of these keying approaches, only properly keyed modules (e.g., modules with properly located alignment holes or alignment notches) are permitted to fully insert into the card cage.